This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This project is designed to characterize young, aged, and middle-aged rhesus monkeys as cognitively normal or impaired. At the outset of each animal's assignment to the project, an MRI scan is performed to determine if the brain is grossly normal. Animals with visible tumors or lesions are screened from the study. Medical records are checked to screen out monkeys that may have prior CNS experimentation, chronic disease, and other characteristics that would make them unsuitable for assignment. Animals are trained on the Wisconsin General Testing Apparatus to make basic responses for food reward. Monkeys are then moved to a series of cognitive tests that have been standard in our laboratory for a number of years. The advantage of standardized tasks is that we can compare current findings with prior findings in our ongoing efforts to identify the neural substrates of cognitive decline. Performance is characterized in a variety of cognitive domains that are characteristic of normal human cognitive aging. These include task learning, visual recognition, spatial working memory, executive and motor function. Following the completion of the standardized task battery, the monkeys are shipped to Boston University, where neurophysiological, immunohistochemical, and neuroanatomical studies are conducted. An important finding in the past project year is that the integrity of the white matter of the cingulum bundle (but not the genu) is correlated with preserved working memory and short-term memory in aging. These findings have important implications for early detection of brain changes that may lead to abnormal function in old age.